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Thermostable Lichenase from Clostridium thermocellum as a Host Protein in the Domain Insertion Approach

O. S. Pavlenko1,a*, O. A. Gra1, O. N. Mustafaev2,b*, K. V. Kabarbaeva1, N. S. Sadovskaya1, A. A. Tyurin1, V. S. Fadeev1, and I. V. Goldenkova-Pavlova1,c*

1Timiryazev Institute of Plant Physiology, Russian Academy of Sciences, 127276 Moscow, Russia

2Baku State University, Department of Biophysics and Molecular Biology, AZ1106 Baku, Azerbaijan

* To whom correspondence should be addressed.

Received March 3, 2019; Revised April 29, 2019; Accepted April 30, 2019
Clostridium thermocellum lichenase (endo-β-1,3;1,4-glucan-D-glycosyl hydrolase, EC (P29716)) has been tested for the insertion of two model fluorescent proteins (EGFP and TagRFP) into two regions of this enzyme. Functional folding of the resulting proteins was confirmed by retention of lichenase activity and EGFP and TagRFP fluorescence. These results convincingly demonstrate that (i) the two experimentally selected lichenase loop regions may serve as the areas for domain insertion without disturbing enzyme folding in vivo; (ii) lichenase permits not only single but also tandem insertions of large protein domains. High specific activity, outstanding thermostability, and efficient in vitro refolding of thermostable lichenase make it an attractive new host protein for the insertional fusion of domains in the engineering of multifunctional proteins.
KEY WORDS: lichenase, fluorescent proteins, single and tandem insertions of proteins

DOI: 10.1134/S0006297919080091